Frequency-changing method and means



March 25, 1930. c. v. LOGWQOD 1,751,485

FREQUENCY CHANGING METHOD AND MEANS Filed May 1. 1924 LOW OLTAGE 4 i a 222% W 22%??? INVENTORI -VZ ogwo0d 7) ORNEY Patented Mar. 25, 1936 PATENT OFFICE CHARLES V. LOGWOOI), OF JERSEY CITY, NEW JERSEY, ASSIG-NOE TO DE FOREST RADIO TELEPHONE & TELEGRAPH COMPANY, OF JERSEY TION OF DELAWARE CITY, NEW JERSEY, A CORPORA- FREQUENCY-CHANGING METHOD AND MEANS Application filed May 1, 1924.

lighting current as the source of current for radio receiving apparatus, but use of said current has resulted in a humming in theradio apparatus, due primarily to the pulsations in the house lighting current. Use of alternating house li hting current has presented the greatest dificulty because of the comparative low frequency of the alternations, that is, usually 60 cycles, which is in the range of audibility and therefore objectionable as the source of electric supplyfor radio receiving apparatus. However, alternating current has a number of advantages such as economy, ease of transformation from one voltage to another, and the very important advantage that it is always ready to use.

The objects of the present invention are to provide a transforming method and means which may be employed with radio receiving apparatus without a resulting hum due to the alternations of the house lighting current employed; to set up radio frequency oscillations; to obtain a flow of current of constant high frequency potential from said radio frequency oscillations; to employ a grid circuit in the frequency changing tubes; to secure simplicity of construction and operation, and to obtain other advantages and results as may be brought out in the following description.

Referring to the accompanying drawing to which reference will be had in the following description the figure illustrates diagrammatically the method and means for chang ing the frequency of alternating current in accordance with my invention.

In the specific embodiment of the invention illustrated in said drawing, the reference numerals 1 and 2 represent the input wires for the apparatus, to supply house lighting current thereto such as the usual Serial No. 710,282.

60 cycles 110 volt alternating current. These wires are connected to the opposite ends of a primary 3 of a multiple transformer. For convenience I have shown a secondary at having a center tap 5 which in effect amounts to two secondaries. Another secondary 6 is provided for lighting the filaments as will be hereinafter explained.

From the outer ends of secondary 4 I make connection to the plates 7 of a pair of transforming tubes 8. In each such connection between secondary and plate is interposed a high frequency choke coil 9. Each plate is also connected to one end of an output pri- .mary 10 the other ends of which are connected to opposite sides of a condenser 11.

input current, but will pass current of radio frequency.

Associated with output primary 10 is an output secondary 12 which I have shown for convenience as in two sections with the inner ends connected by wire 13. The outer ends of this output secondary 12 are connected by wires 14 to the filaments of radio receiving apparatus (not shown). Preferably a condenser 15 is connected across the outer end connections of said output secondary. Another secondary 16 is associated with output primary 10 for purposes hereinafter menso tioned.

The tubes 8 have, in addition to plates 7, each a filament 17 and a grid 18. I have shown the corresponding filament terminals connected and the connections separately joined with the opposite ends of the light secondary 6 of the input transformer. One of the filament connections, as 19, is also attached to one side of an absorbing condenser 20'the other side of which is in circuit with the center tap 5 of the input secondary. The other filament connection 21 is in circuit with a resistance or grid leak 22 in turn connected with a center tap 23 from the secondary 16 of the output transformer. The outer ends of said secondary16 are connected to the and plate to filament which is therefore free to pass through the otherwise interrupting condenser 11, thus obtaining the radio frequency current in the output transformer and setting up the output current in the secondary 12 to the radio receiving apparatus. Emphasis is to be laid on the fact that choke coils 9 prevent the high frequency current from going back through the input secondary 4 and condenser 11 prevents the low frequency current from short circuiting through the ouput primary. The output current from output secondary 12 is suitable for lighting a filament in a radio receiving apparatus, but may be and is preferably passed through a further rectifier so as to obtain a low voltage rectified current if desired. I have not deemed it necessary to specifically show a rectifier from the output secondary as any suitable type of rectifier may be used.

Attention is to be called to the fact that the absorbing condenser is charged at all times by the rectified current, the positive side of the condenser being toward the filament and the negative toward the center tap of the transformer secondary. For taking off a further supply of rectified current, leads 24k, 25 may be connected from opposite sides of the absorbing condenser 20. One lead, as 25, may have a variable resistance or potentiometer 26 at the end thereof connected across to the other lead 24:. From the potentiometer 26- connection is made with a choke coil 27 beyond which is a condenser 28 across to the other lead and then a further choke coil 29 for trapping and filtering the undesirable pulsations and thus enabling the device to operate as the source of supply for direct current.

Obviously detail changes and modifications may be made in the manufacture and use of my improved method and means for rectifying alternating current, and I do not Wish to be understood as limitingmyself to the exact structure shown except as set forth in the following claim when construed in the light of the prior art. I

Having thus described my invention, I claim In an alternating current frequency changing system the combination with a source of low frequency current of a plurality of vacuum tube oscillators connected to said source, a high frequency output circuit connected to said oscillators and alow voltage circuit inductively related with said high frequency output circuit, the inductive relation being effected by a transformer having a primary of two portions connected through a low frequency choking condenser and another primary winding connected in the grid filament circuit of the oscillators.

' CHARLES V. LQGWOQD. 

